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  <div class="question_difficulty">
   难度：Medium
  </div>
  <div>
   <h1 class="question_title">
    90. Subsets II
   </h1>
   <p>
    Given a collection of integers that might contain duplicates,
    <strong>
     <em>
      nums
     </em>
    </strong>
    , return all possible subsets (the power set).
   </p>
   <p>
    <strong>
     Note:
    </strong>
    The solution set must not contain duplicate subsets.
   </p>
   <p>
    <strong>
     Example:
    </strong>
   </p>
   <pre>
<strong>Input:</strong> [1,2,2]
<strong>Output:</strong>
[
  [2],
  [1],
  [1,2,2],
  [2,2],
  [1,2],
  []
]
</pre>
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  <div>
   <h1 class="question_title">
    90. 子集 II
   </h1>
   <p>
    给定一个可能包含重复元素的整数数组
    <em>
     <strong>
      nums
     </strong>
    </em>
    ，返回该数组所有可能的子集（幂集）。
   </p>
   <p>
    <strong>
     说明：
    </strong>
    解集不能包含重复的子集。
   </p>
   <p>
    <strong>
     示例:
    </strong>
   </p>
   <pre><strong>输入:</strong> [1,2,2]
<strong>输出:</strong>
[
  [2],
  [1],
  [1,2,2],
  [2,2],
  [1,2],
  []
]</pre>
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